Δ5-desaturase belongs to the family of “front-end” desaturases. In addition to Δ5-desaturase, the family also includes Δ4-, Δ6-, and Δ8-desaturases. These desaturases introduce double-bonds between the carboxyl end (i.e., the “front end”) and a pre-existing double bond in fatty acids. This is a required step in the biosynthesis of polyunsaturated fatty acids (PUFAs) such as arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).
ARA, EPA, and DHA are oils widely used in nutritional products. The current sources of these oils are very expensive and non-renewable. The production of oils enriched in ARA, EPA, and DHA from transgenic plants or oleaginous microorganisms expressing heterologous front-end desaturases offers a low-cost, renewable alternative to purifying the oils from natural sources. Transgenic organisms producing these oils are currently in development. See U.S. Pat. Nos. 6,635,451; 7,067,285; and 7,241,619.
Before commercialization of ARA-, EPA-, or DHA-enriched oils derived from transgenic organisms can begin, approval is needed from such regulatory agencies as the United States Food and Drug Administration (FDA) and the United States Department of Agriculture (USDA).
One regulatory requirement for transgenic plants is to detect and quantitate the specific transgenic proteins present in the organism, including the oil-rich seeds.
However, quantitation of the front-end desaturases is a problem because specific antibodies to the desaturases do not exist. The most straightforward way to produce an antibody against a protein is to use the protein itself as an immunogen. This is not possible with the front-end desaturases. All the front-end desaturases are highly hydrophobic; they contain several transmembrane domains and reside in the microsomal membranes of cells (Pereira S L, Leonard A E, Mukerji P. (2003) Recent advances in the study of fatty acid desaturases from animals and lower eukaryotes. Prostaglandins Leukot Essent Fatty Acids. 68 (2):97-106). The hydrophobic nature of the front-end desaturases makes large-scale purification of them a challenge. As a result, the full-length proteins cannot be used as immunogens in antibody production.
The production of antibodies that specifically recognize a front-end desaturase, such as 45-desaturase, would enable one to identify and quantitate the enzyme in various systems. This would be especially useful when a Δ5-desaturase gene is expressed in a transgenic host (such as a plant, yeast, or mammalian cell) during production of PUFA-enriched oils. A need therefore exists for antibodies that specifically recognize Δ5-desaturase.